"""The other direction: .sab -> .sax, ported from sedona.offline.OfflineApp
(decodeAppBinary + encodeAppXml) and OfflineComponent/OfflineLink.

Output is meant to match `sedonac.exe <file.sab>` byte for byte, down to the
`<!-- /path -->` comments and Java's float formatting.

Note what a .sab simply does not contain: only *config* props are stored, so
runtime prop values cannot come back. sedonac has the same hole -- both write
the manifest default for them, and a value equal to its default is not written
at all.
"""
import os, struct, base64, math, datetime
import sab, config


class Reader:
    def __init__(self, data):
        self.b, self.p = data, 0

    def take(self, n):
        if self.p + n > len(self.b):
            raise Exception("truncated sab at offset %d" % self.p)
        v = self.b[self.p:self.p + n]
        self.p += n
        return v

    def u1(self): return self.take(1)[0]
    def u2(self): return struct.unpack(">H", self.take(2))[0]
    def i4(self): return struct.unpack(">i", self.take(4))[0]
    def i8(self): return struct.unpack(">q", self.take(8))[0]
    def f4(self): return struct.unpack(">f", self.take(4))[0]
    def f8(self): return struct.unpack(">d", self.take(8))[0]

    def str_(self):
        end = self.b.index(0, self.p)
        s = self.b[self.p:end].decode("ascii")
        self.p = end + 1
        return s


# ---------- values ----------
def decode_value(r, vtype, flags):
    if "s" in flags:                                   # asStr Buf: u2 len (incl NUL)
        n = r.u2()
        return r.take(n).split(b"\0")[0].decode("ascii")
    if vtype == "bool":
        v = r.u1()
        return None if v == 2 else (v == 1)
    if vtype == "byte":   return r.u1()
    if vtype == "short":  return r.u2()
    if vtype == "int":    return r.i4()
    if vtype == "long":   return r.i8()
    if vtype == "float":  return r.f4()
    if vtype == "double": return r.f8()
    if vtype in ("sys::Buf", "buf"):
        return bytes(r.take(r.u2()))
    raise Exception("unhandled slot type " + str(vtype))


def default_value(vtype, flags, raw):
    """The manifest `default`, or Value.defaultForType -> zero. Same rules as sab.py."""
    if "s" in flags:
        return raw or ""
    if vtype == "bool":
        return None if raw == "null" else raw in ("true", "1")
    if vtype in ("byte", "short", "int", "long"):
        return sab._int(raw)
    if vtype == "float":
        # the default is a 32-bit Float too, so round before comparing:
        # 0.1 as a double is not the 0.1 that came out of the file
        return to_f32(sab._flt(raw))
    if vtype == "double":
        return sab._flt(raw)
    if vtype in ("sys::Buf", "buf"):
        return base64.b64decode(raw) if raw else b""
    raise Exception("unhandled slot type " + str(vtype))


def same(a, b):
    if isinstance(a, float) and isinstance(b, float):
        return (math.isnan(a) and math.isnan(b)) or a == b
    return type(a) is type(b) and a == b


# ---------- java number formatting ----------
F32_MAX = 3.4028234663852886e38          # largest finite float
F32_INF_EDGE = 3.4028235677973366e38     # midpoint to 2**128: below rounds to F32_MAX


def to_f32(v):
    """Round a double to the nearest float. struct raises past F32_MAX instead
    of rounding, so handle that edge ourselves."""
    try:
        return struct.unpack(">f", struct.pack(">f", v))[0]
    except OverflowError:
        if abs(v) < F32_INF_EDGE:
            return math.copysign(F32_MAX, v)
        return math.copysign(math.inf, v)


def _shortest(a, single):
    """Fewest digits that still round-trip -- what Java's Float/Double.toString picks."""
    for prec in range(0, 17):
        s = "%.*e" % (prec, a)
        v = float(s)
        if single:
            v = to_f32(v)
        if v == a:
            break
    mant, exp = s.split("e")
    digits = mant.replace(".", "").rstrip("0") or "0"
    return digits, int(exp)


def java_float(v, single=True):
    """Java Float.toString / Double.toString: always a decimal point, E-form
    outside [1e-3, 1e7)."""
    if math.isnan(v):
        return "NaN"
    if math.isinf(v):
        return "-Infinity" if v < 0 else "Infinity"
    neg = math.copysign(1.0, v) < 0
    a = abs(v)
    if a == 0.0:
        return "-0.0" if neg else "0.0"

    digits, exp = _shortest(a, single)
    if -3 <= exp < 7:
        if exp >= 0:
            head = digits[:exp + 1].ljust(exp + 1, "0")
            tail = digits[exp + 1:] or "0"
        else:
            head, tail = "0", "0" * (-exp - 1) + digits
        out = head + "." + tail
    else:
        out = digits[0] + "." + (digits[1:] or "0") + "E" + str(exp)
    return "-" + out if neg else out


def encode_string(val, vtype, flags):
    """Value.encodeString()."""
    if "s" in flags:
        return _literal(val)
    if vtype == "bool":
        return "null" if val is None else ("true" if val else "false")
    if vtype == "float":
        return "null" if math.isnan(val) else java_float(val, True)
    if vtype == "double":
        return "null" if math.isnan(val) else java_float(val, False)
    if vtype in ("sys::Buf", "buf"):
        return base64.b64encode(val).decode("ascii")
    return str(val)


def _literal(s):
    """TextUtil.toLiteral."""
    out = []
    for c in s:
        out.append({"\0": "\\0", "\n": "\\n", "\r": "\\r", "\t": "\\t",
                    "\\": "\\\\", '"': '\\"', "$": "\\$"}.get(c, c))
    return "".join(out)


def _safe(s):
    """XWriter.safe: escape markup, quotes, and anything outside printable ASCII."""
    out = []
    for c in s:
        o = ord(c)
        if o < 0x20 or o > 0x7e or c in "'\"":
            out.append("&#x%x;" % o)
        elif c == "<":
            out.append("&lt;")
        elif c == ">":
            out.append("&gt;")
        elif c == "&":
            out.append("&amp;")
        else:
            out.append(c)
    return "".join(out)


# ---------- binary decode ----------
def read_app(sab_path, home):
    """-> (kits, comps by id, links). Each comp: id/type/name/parent/kids/props."""
    r = Reader(open(sab_path, "rb").read())
    if r.i4() != 0x73617070:
        raise Exception("%s is not a .sab (bad magic)" % sab_path)
    ver = r.i4()
    if ver != 0x0003:
        raise Exception("unsupported sab version 0x%x" % ver)

    parts = []
    for _ in range(r.u1()):
        name = r.str_()
        parts.append((name, "%08x" % (r.i4() & 0xFFFFFFFF)))
    kits, types_by_q = sab.load_kits(parts, home)
    r.u2()                                      # maxId, recomputed on the way out

    qname_of = {}
    for ki, (kname, _, tlist) in enumerate(kits):
        for t in tlist:
            qname_of[(ki, int(t.get("id")))] = "%s::%s" % (kname, t.get("name"))

    cache = {}
    by_id, order = {}, []
    while True:
        cid = r.u2()
        if cid == 0xFFFF:
            break
        ki, ti = r.u1(), r.u1()
        if (ki, ti) not in qname_of:
            raise Exception("comp %d: no type %d in kit %d" % (cid, ti, ki))
        qname = qname_of[(ki, ti)]
        c = {"id": cid, "type": qname, "name": r.str_(), "kids": [], "props": []}
        c["parentId"], c["childId"], c["siblingId"] = r.u2(), r.u2(), r.u2()
        for name, vtype, flags, dflt in sab.resolve_slots(qname, types_by_q, cache):
            if "a" in flags or "c" not in flags:
                continue                        # config props only, in slot-id order
            c["props"].append((name, vtype, flags, dflt, decode_value(r, vtype, flags)))
        if r.u1() != ord(";"):
            raise Exception("corrupted component %d %s" % (cid, c["name"]))
        if cid in by_id:
            raise Exception("duplicate id: %d" % cid)
        by_id[cid] = c
        order.append(cid)

    # rebuild the tree from the child/sibling id chain
    for c in by_id.values():
        c["parent"] = by_id[c["parentId"]] if c["parentId"] != 0xFFFF else None
        if c["childId"] != 0xFFFF:
            kid = by_id[c["childId"]]
            while True:
                c["kids"].append(kid)
                if kid["siblingId"] == 0xFFFF:
                    break
                kid = by_id[kid["siblingId"]]

    links = []
    while True:
        fc = r.u2()
        if fc == 0xFFFF:
            break
        fs, tc, ts = r.u1(), r.u2(), r.u1()
        for cid in (fc, tc):
            if cid not in by_id:
                raise Exception("link references unknown comp id %d" % cid)
        links.append((by_id[fc], fs, by_id[tc], ts))
    if r.u1() != ord("."):
        raise Exception("invalid app end marker")

    return kits, by_id, order, links, types_by_q, cache


# ---------- xml encode ----------
def path_of(c):
    parts = []
    while c["parent"] is not None:
        parts.append(c["name"])
        c = c["parent"]
    return "/" + "/".join(reversed(parts)) if parts else "/"


def write_xml(out, kits, app, links, types_by_q, cache):
    w = out.append
    w("<?xml version='1.0'?>\n")
    w("<sedonaApp>\n")
    w("<schema>\n")
    for name, cks, _ in kits:
        w('  <kit name="%s" checksum="%08x" />\n' % (_safe(name), cks & 0xFFFFFFFF))
    w("</schema>\n")

    w("<app>\n")
    write_props(w, app, 2)
    for kid in app["kids"]:
        write_comp(w, kid, 2)
    w("</app>\n")

    w("<links>\n")
    for fc, fs, tc, ts in links:
        w('  <link from="%s.%s" to="%s.%s"/>\n' % (
            _safe(path_of(fc)), _safe(slot_name(fc, fs, types_by_q, cache)),
            _safe(path_of(tc)), _safe(slot_name(tc, ts, types_by_q, cache))))
    w("</links>\n")
    w("</sedonaApp>\n")


def slot_name(comp, slot_id, types_by_q, cache):
    slots = sab.resolve_slots(comp["type"], types_by_q, cache)
    if slot_id >= len(slots):
        raise Exception("%s has no slot id %d" % (comp["type"], slot_id))
    return slots[slot_id][0]


def write_props(w, c, indent):
    """Only props whose value differs from the slot default get written."""
    n = 0
    for name, vtype, flags, dflt, val in c["props"]:
        if same(val, default_value(vtype, flags, dflt)):
            continue
        w('%s<prop name="%s" val="%s"/>\n' % (
            " " * indent, _safe(name), _safe(encode_string(val, vtype, flags))))
        n += 1
    return n


def write_comp(w, c, indent):
    pad = " " * indent
    w("%s<!-- %s -->\n" % (pad, path_of(c)))
    w('%s<comp name="%s" id="%d" type="%s"' % (pad, _safe(c["name"]), c["id"], _safe(c["type"])))

    body = []
    n = write_props(body.append, c, indent + 2)
    for kid in c["kids"]:
        write_comp(body.append, kid, indent + 2)
    if not n and not c["kids"]:
        w("/>\n")
    else:
        w(">\n")
        w("".join(body))
        w("%s</comp>\n" % pad)


# ---------- main ----------
def default_sax_name(sab_path):
    """`app.sab` -> `app-sab2sax-20260728-140609.sax`."""
    stem = os.path.splitext(os.path.basename(sab_path))[0]
    stamp = datetime.datetime.now().strftime("%Y%m%d-%H%M%S")
    return "%s-sab2sax-%s.sax" % (stem, stamp)


def decode(sab_path, home=None, sax_path=None):
    if home is None:
        home = config.get_sedona_home()
    if sax_path is None:
        sax_path = os.path.join(os.path.dirname(os.path.abspath(sab_path)),
                                default_sax_name(sab_path))

    kits, by_id, order, links, types_by_q, cache = read_app(sab_path, home)
    if 0 not in by_id:
        raise Exception("no app component (id 0) in " + sab_path)

    out = []
    write_xml(out, kits, by_id[0], links, types_by_q, cache)
    text = "".join(out)
    with open(sax_path, "w", encoding="ascii", newline="\n") as f:
        f.write(text)
    return len(text)